Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$70.43	10.126%	$77.5617	$77.56	$77.55	$77.60
Purchase #2	$50.94	6.605%	$54.3046	$54.30	$54.30	$54.30
Purchase #3	$49.83	11.578%	$55.5993	$55.60	$55.60	$55.60
Purchase #4	$224.55	5.219%	$236.2693	$236.27	$236.25	$236.30
Purchase #5	$119.70	12.411%	$134.556	$134.56	$134.55	$134.60
Purchase #6	$235.46	4.278%	$245.533	$245.53	$245.55	$245.50
Purchase #7	$174.81	12.312%	$196.3326	$196.33	$196.35	$196.30
7 purchase totals =	$925.72		$1,000.1565	$1,000.15	$1,000.15	$1,000.20